The exhaust note is rather delicious too, Alpina’s modifications gifting noises that are endlessly entertaining to listen to

Everything about the B6 is, shall we say, large. Beneath its bonnet sits a twin-turbo 4.4-litre V8 that produces 591bhp between 5200 and 6250rpm and a positively herculean 590lb ft at 3500rpm.

The gearbox is a tweaked version of the eight-speed ZF automatic used in the regular 6 Series, in this case enhanced by Alpina’s engineers to prevent upshifts in certain modes (which is useful on a circuit, for example) and to momentarily cut the flow of fuel and deliver a lovely burble between gearshifts as a result.

The chassis has also been preened by Alpina to provide a wider range of set-ups than in the standard BMW 6 Series. So in Comfort mode the ride quality is softer than you get in a regular BMW, while in Sport and Sport Plus it’s the other way around, with the electronic dampers sharpening up the driving experience to a level that no regular BMW driver would quite recognise.

The same philosophy applies to the interior, in which you’ll find a far higher quality of leather than in a factory BMW, plus a set of dials and seats that are bespoke to the B6. The monstrous Alpina also comes with dual-zone climate control, electrically adjustable and heated front seats, cruise control, a quad-pipe titanium Akrapovic exhaust system, LED head and fog lights, a limited slip differential, parking sensors, and 20in alloy wheels as standard. Quite a handsome list, plus the inclusion of BMW's iDrive infotainment system with a 10.2in display, sat nav, USB connectivity, DAB radio and a built-in Wi-fi hotspot.

And if that’s not sufficient to distinguish the car, Alpina also offers a vast range of options that enable B6 owners to personalise their cars to whatever specification they require – while spending a great deal of money in the process, of course.

Outwardly, you can pick a B6 from lesser 6 Series for several reasons. Not only does it come with Alpina’s big, beautiful 20in turbine alloys, but there’s also a new front splitter that reduces lift by as much as 10 percent, says Alpina, while at the back there’s a small new lip spoiler or, if you’re feeling flamboyant, an optional new tea-tray wing that makes even better use of the redesigned rear diffuser.

On the road the B6 feels massively rapid, thanks mainly to the torque it produces from seemingly any engine speed and in any gear. The way the transmission manages the flow of energy is truly epic, and it gives the B6 a blend of smooth but monumental acceleration that no factory BMW, not even the M6, could hope to replicate on the move.

The exhaust note is rather delicious too, Alpina’s modifications gifting the B6 with a depth and range of noises that are endlessly entertaining to listen to.

Despite the chassis modifications, the B6 always feels like a fairly big car on the move. Its kerb weight of 1870kg means it is always going to fight a losing battle against the forces of inertia that swell during rapid direction changes or, indeed, under braking.

The steering is a touch distant in its feedback, too, even though the front end always feels planted – as does the tail – if and when you aim the B6 at a high-speed corner with some enthusiasm.

Overall, the B6 is more of a high-speed cruiser than it is a pure sports car, but for the kind of customer who wants that little bit more depth from their 6 Series, it’s a lovely alternative to the factory offerings.

At £96,950 for the coupé and £101,950 for the convertible , it’s expensive, yes, but if ever a car felt worth that sort of money, the Alpina B6 is it.